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No, he was simply pointing out that no one is afraid to contemplate laws of physics in which energy is not conserved, which you seemed to be implying.

my apologies if my words were misleading in that direction: i did NOT intend to imply anything of the sort! there are nice counterexamples in the 40's/50's where energy only "statistically conserved."

rather i argued (#18) that no one has "showed conservation of energy", and that it is currently inconceivable that one ever will in many relevant macroscopic scenarios.

TubbaBlubba repeatedly (#19, #24, and i had thought in #38) made naive claims claiming the absence of evidence as evidence of absence
(as you noted in #20).

i took his #38 as supporting Cuddles #30 claim that showing conservation of energy on planetary scales was "quite easy really. Conservation of energy is one of the fundamental bases of all our ideas about physics." which fails Logic 101 as an argument. i first read TubbaBlubba's post as supporting that falasy; i now see he might have intended something else.

my apologies if my words were misleading in that direction: i did NOT intend to imply anything of the sort! there are nice counterexamples in the 40's/50's where energy only "statistically conserved."

rather i argued (#18) that no one has "showed conservation of energy", and that it is currently inconceivable that one ever will in many relevant macroscopic scenarios.

TubbaBlubba repeatedly (#19, #24, and i had thought in #38) made naive claims claiming the absence of evidence as evidence of absence
(as you noted in #20).

i took his #38 as supporting Cuddles #30 claim that showing conservation of energy on planetary scales was "quite easy really. Conservation of energy is one of the fundamental bases of all our ideas about physics." which fails Logic 101 as an argument. i first read TubbaBlubba's post as supporting that falasy; i now see he might have intended something else.

what was your intention TubbaBlubba?

My intention is to not discuss science with people who believe science requires formal logical proofs of theories.

__________________"The presidentís voracious sexual appetite is the elephant that the president rides around on each and every day while pretending that it doesnít exist." - Bill O'Reilly et al., Killing Kennedy

I'm fairly sure planets suddenly being governed by different laws of physics would've been discovered by now.

Deep out in the cosmos, it's tougher, but AFAIK no one has yet come up with a theory that explains the cosmos better than general relativity, which more or less assumes the cosmological principle. Until someone does or it turns on we can't explain the physics of say, distant stars using our established laws, I think we can assume the principle holds true.

__________________"The presidentís voracious sexual appetite is the elephant that the president rides around on each and every day while pretending that it doesnít exist." - Bill O'Reilly et al., Killing Kennedy

the question is an empirical one, limits to what we can measure which apply as much to the earth and the moon as anywhere else.

the point is that while we have stong evidence placinfg constraints on the conservation of energy in the lab, we have no such evidence, nor can we conceive of an experiment that would provide such evidence, that energy is conserved on planetary scales, or "in the sun".

we often do a thought experiment: considering a large sphere around the moon, and argue that the energy moving in through this surface minus the energy moving out, plus the increase in energy inside will sum to zero.
i am not arguing that this is not true; merely pointing out that we have no empirical evidence that it is true. violations vastly greater than those we can rule out in the lab would be undetectable.

we have faith in the conservation of energy on these scales, we believe it holds, but the evidence for it absent.

Originally Posted by TubbaBlubba

I'm fairly sure planets suddenly being governed by different laws of physics would've been discovered by now.

A similar argument suggests that we don't have evidence that conservation of energy holds when I am wearing a tutu (I've never worn a tutu)

__________________"... when people thought the Earth was flat, they were wrong. When people thought the Earth was spherical they were wrong. But if you think that thinking the Earth is spherical is just as wrong as thinking the Earth is flat, then your view is wronger than both of them put together."
Isaac Asimov

the point is that while we have stong evidence placinfg constraints on the conservation of energy in the lab, we have no such evidence, nor can we conceive of an experiment that would provide such evidence, that energy is conserved on planetary scales, or "in the sun".

That's not really true. The evidence is less direct, but it's not nonexistent.

In particular, there's a very rigorous mathematical theorem which states that for every symmetry in your physical laws there will be a corresponding conservation law. The fact that our laws of physics are translation-invariant (meaning the laws of physics don't vary from location to location) leads to momentum conservation, for example. And the fact that our laws of physics are time-independent leads to the conservation of energy.

If conservation of energy is to be violated, that will require that the laws of physics vary in time. And that would produce signs other than just the violation of energy conservation. It's true that variations could always be too small to observe (but the energy conservation violations would then be correspondingly small), but that problem exists whether you're talking about experiments in lab or observations of distant astronomical phenomena. Our precision may be greater in the lab, but the basic problem remain the same.

__________________"As long as it is admitted that the law may be diverted from its true purpose -- that it may violate property instead of protecting it -- then everyone will want to participate in making the law, either to protect himself against plunder or to use it for plunder. Political questions will always be prejudicial, dominant, and all-absorbing. There will be fighting at the door of the Legislative Palace, and the struggle within will be no less furious." - Bastiat, The Law

It's true that variations could always be too small to observe (but the energy conservation violations would then be correspondingly small), but that problem exists whether you're talking about experiments in lab or observations of distant astronomical phenomena. Our precision may be greater in the lab, but the basic problem remain the same.

i agree that the basic problem remains the same. apologies if i spoke loosely.

there does seem to be a difference between measurements on the lab, where we can work vary hard to find inconsistency and have not yet found it, and measurements on the scale of a planet which we have never attempted and for which we can only conceive (today) of obtaining a very loose bound on consistency. of course today's laws of physics give us no reason to expect anything different on planetary scales... and defending that last statement leads to circularity.

of course today's laws of physics give us no reason to expect anything different on planetary scales... and defending that last statement leads to circularity.

Certain kinds of changes in the laws of physics from one location to another will show up even over vast distances. In particular, atomic and molecular spectra are sensitive to the laws of quantum mechanics, and unless the changes happen in very specific ways (or below our detection threshold), then we could see signs of it. That doesn't preclude any possible position dependence to the laws of physics, but it does constrain such changes. Beyond that, though, it's not so much circularity as it is Occam's Razor. The simplest scenario would be universal laws of physics, that accurately describes what we can currently observe, so that's a preferable model to one in which the laws of physics are not universal. Occam's Razor doesn't tell you that the simpler explanation is correct (or even that it's more likely to be correct), but it does tell you to stick with simplicity until it's inadequate. That time has not arrived.

__________________"As long as it is admitted that the law may be diverted from its true purpose -- that it may violate property instead of protecting it -- then everyone will want to participate in making the law, either to protect himself against plunder or to use it for plunder. Political questions will always be prejudicial, dominant, and all-absorbing. There will be fighting at the door of the Legislative Palace, and the struggle within will be no less furious." - Bastiat, The Law

Certain kinds of changes in the laws of physics from one location to another will show up even over vast distances.

yes, i agree. and i also agree with your example.
other "kinds of changes" we cannot detect even locally. i am happy to note both "kinds."

Originally Posted by Ziggurat

Occam's Razor doesn't tell you that the simpler explanation is correct (or even that it's more likely to be correct), but it does tell you to stick with simplicity until it's inadequate. That time has not arrived.

could you help me see how this is relevant to the point in play. i see how it is relevant to rather marvelous evidence that atomic transitions in remote parts of the universe we can see are described by the same "laws of physics" we observe in the lab.

the question is an empirical one, limits to what we can measure which apply as much to the earth and the moon as anywhere else.

the point is that while we have stong evidence placinfg constraints on the conservation of energy in the lab, we have no such evidence, nor can we conceive of an experiment that would provide such evidence, that energy is conserved on planetary scales, or "in the sun".

Unless I've missed something, we can indeed conceive of measurements which place very tight constraints on any possible violations of conservation of energy on a planetary scale. Those measurements have been carried out for some centuries now and are called, collectively, "astronomy".

Assuming that energy and orbital period are related, the existence of a fossil record going back more than 4 billion years suggests that the earth's orbit has remained more or less constant during that time, and 4 billion years is a _long_ time for variations to accumulate. Similarly, historical records of eclipses provide a fairly precise lower bound on such deviations, since the thing about changing orbital period is that the changes in observed position of the orbiting bodies will accumulate.

Now, it's possible that conservation of energy is violated in a cyclical fashion, so that the planetary orbits change first in one direction, then in the other, but in the absence of evidence to support (or even suggest) this, the afore-mentioned Occam's Razor would seem to apply.

Assuming that energy and orbital period are related, the existence of a fossil record going back more than 4 billion years suggests that the earth's orbit has remained more or less constant during that time, and 4 billion years is a _long_ time for variations to accumulate. Similarly, historical records of eclipses provide a fairly precise lower bound on such deviations, since the thing about changing orbital period is that the changes in observed position of the orbiting bodies will accumulate.

Agreed, that is a long time. And if we put a number on "more or less" constant, we could place a bound on the loss of "orbital energy" with time, taking into account the retreat of the moon etc.

while the uncertainties in that calculation would, I expect, not provide evidence for an exact balance, it would rule out quite significant departures from (exact) conservation in that case. I was not thinking of "orbital energy" in my posts above, but your example fits.

Again, I am not arguing that energy is not conserved, and i would certainly argue that it is profitable to assume it is conserved. Nevertheless, on large spatial scales this assumption has v little direct empirical support.